CNN  — 

Moderna will expand the size of its Covid-19 vaccine trial in younger children, the company said Monday, and will not seek emergency use authorization for the vaccine in that age group until later this year or early next year.

“We are actively discussing a proposal with the FDA. The objective is to enroll a larger safety database which increases the likelihood of detecting rarer events,” Moderna spokesperson Ray Jordan said in a statement to CNN.

The original size of the trial was 6,750 children ages 6 months to 12 years. Moderna did not say how many additional children the trial will now include.

Jordan said Moderna would likely seek authorization for the vaccine in “winter 2021/early 2022.” Moderna’s vaccine is currently authorized for people ages 18 and older, and it is seeking authorization for people ages 12 to 17.

The New York Times reported on Monday that Pfizer will also expand its vaccine trials in younger children. It cited multiple people familiar with the two companies’ pediatric vaccine trials who said the US Food and Drug Administration found the trials were too small to detect rare side effects.

The FDA did not immediately return CNN’s request for comment.

A Pfizer representative told CNN on Monday it has no updates to it previous timelines or details about its pediatric trial. Pfizer noted it began testing its Covid-19 vaccine in people ages 5 to 11 in on June 8 and in those younger than 5 starting on June 21, and said its trial would include up to 4,500 participants in the United States, Finland, Poland and Spain.

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Pfizer has said it expects initial results of the Phase 2/3 trials in September for children 5 to 11, and results for younger children shortly after.

Many parents are eager to vaccinate younger children as schools prepare to open for in-person learning in the fall. Pfizer vaccine is currently authorized for people as young as 12, but there’s no vaccine available for younger children.

President Joe Biden said last week that children under the age of 12 could be eligible to receive a Covid-19 vaccine “soon,” predicting the shot could get the green light in the next few months. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told CNN’s Jim Acosta earlier this month that “the final decision is going to be up to the FDA. And I would imagine that likely will not happen until we get well into the winter, towards the end of this year.”